The first accident took place near the town of Etawah, about 170 miles (270 kilometers) southwest of Lucknow, the capital of Uttar Pradesh state, when a train entering a station rammed another train that had stopped there. Ten people, including the driver of one of the trains, were injured, according to Brij Lal, a senior police official.

A second similar accident occurred near Kanpur, about 60 miles (100 kilometers) southwest of Lucknow, and left 10 people dead and 37 others injured, some seriously, Lal said.

“Both these accidents were due to dense fog,” said railway official N.K. Srivastava. He said the trains were traveling at low speeds in both accidents.

Fog, which is a usual winter occurrence across northern India, has disrupted railway schedules across Uttar Pradesh, Srivastava said.

Fog also delayed dozens of domestic and international flights in and out of New Delhi, the Press Trust of India news agency reported.